British Journal of Orthodontics
ISSN: 0301-228X (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/yjor19
Class III Malocclusion: Surgery or Orthodontics? W. J. S. Kerr M.D.S., D.Orth., F.D.S., F.F.D., S. Miller B.D.S., F.D.S. & J. E. Dawber To cite this article: W. J. S. Kerr M.D.S., D.Orth., F.D.S., F.F.D., S. Miller B.D.S., F.D.S. & J. E. Dawber (1992) Class III Malocclusion: Surgery or Orthodontics?, British Journal of Orthodontics, 19:1, 21-24, DOI: 10.1179/bjo.19.1.21 To link to this article: http://dx.doi.org/10.1179/bjo.19.1.21
Published online: 21 Jun 2016.
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Date: 25 September 2016, At: 15:53
British Journal of Orthodontics/ Vol. 19/1992/21-14
Class III Malocclusion: Surgery or Orthodontics? W. J. S. KERR, M.D.S., D.ORTH., F.D.S., F.F.D. S. MILLER, B.D.S., F.D.S.
J. E. DAWBER Department of Orthodontics, Glasgow Dental Hospital and School, 378 Sauchiehall Street, Glasgow G2 3JZ Received for publication January 1991
Abstract. The pre-treatment lateral cephalograms of two groups of 20 subjects with severe Class Ill malocclusions were compared. One group had been considered suitable for orthodontic correction by the diagnosing clinician and the other offered orthognathic surgery. The most sign(ficant d(fferences between the groups were in angle ANB, M/ M ratio (P < 0·001), lower incisor inclination and Holdaway angle (P < 0·01). Threshold values .for angle AN Band lower incisor angulation below which surgery was almost always carried out were -4 and 83 degrees, respectively. Index words: Class III, Surgery, Orthodontic Appliances.
Introduction Surgery and orthodontics are not normally alternative treatments for the same Class III malocclusion. The decision as to which form of treatment is allocated to such patients is made with reference to the severity of the malocclusion and the prognosis for its correction by orthodontic means. Factors which are generally thought to influence the prognosis for orthodontic correction of anterior cross-bite are the degree of antero-posterior and vertical skeletal discrepancy, the inclination of the incisors and the depth of the overbite. A mild skeletal discrepancy, near normal inclination of the upper and lower incisors, which permits the appropriate adjustment of their angulations, and an initial overbite, deep enough to remain to some extent after correction of any anterior crossbite, are seen as favourable indicators of a good prognosis. The age of the patient and the potential for skeletal growth are also of significance in Younger individuals. The perception by the patient of their condition is an important additional factor, as in some cases the profile, rather than the malocclusion, is the principal cause of concern. Although the soft tissue profile may be improved to some degree by orthodontic treatment (Kerr and TenHave, 1987) the change may be too subtle to be appreciated by the untrained eye (Kerr and O'Donnell, 1990). Orthodontic appliances (fixed, functional, and 030 I· 228X/92/004000 + 00502.00
removable) generally bring about the correction of anterior cross-bite by varying amounts ofproclination of upper incisors and retroclination of lower incisors, combined with a degree of backward rotation of the mandible (Kerr and Ten Have, 1988). Proffitt and Ackerman ( 1985) have postulated the concept of three 'envelopes of discrepancy' representing the limits for what can be corrected variously by, orthodontic treatment alone, orthodontic treatment with growth and surgical treatment. Although no data was presented, the limits for incisal movement in the non-growing Class III cases would be an advance of 2 mm for the upper incisors combined with retraction of the lower incisors by 3 mm. The equivalent values for surgical movement were 10 and 25 mm. As far as orthodontic correction is concerned the initial incisor inclination will influence how much movement can be achieved and, hence, this knowledge alone is insufficient to be of much clinical assistance. The aim of this study was, therefore, to try and establish some cephalometric yardsticks which would enable the 'surgery or orthodontics' decision to be taken in a more objective way.
Materials The materials consisted of the pre-treatment lateral cephalograms of 40 patients, equally divided by sex, taken at the Glasgow Dental Hospital and Cannies(!) 1992 British Society for the Study of Orthodontics
22 W. J. S. Kerr eta/. TABLE I
BJO Vol. 19 No. I
Details of subjects included in the study
Males Females Total Mean age (years)
Surgery group
Orthodontics group
10 10 20 17·2± 1·6
10 10 20 14·1± 1·5
burn Hospital, who had been offered either surgical or orthodontic correction of their Class Ill malocclusion. The surgical group had all been seen by an orthodontist, who made the initial decision as to the need for surgery. The orthodontic group were among subjects successfully treated orthodontically forming part of a study previously reported (Kerr and TenHave, 1988). So that the malocclusions were of roughly comparable severity only subjects with negative overjets were included. The details are given in Table 1. Methods
Because two cephalostats with different magnification factors were used in taking the radiographs, and to eliminate sex differences due to size, points and measures were chosen to compare angular and proportional dimensions only. Twenty cephalometric points were digitized on each radiograph and these are demonstrated in Fig. 1. The definitions for these points are as described by Riolo et a/. ( 1974). Using PCDIG (McWilliam, 1989), a computer program which permits the construction of userdefined analyses, the following measurements were derived: SNA, SNB, ANB, M/M ratio, BaSN (cranial base angle), gonia) angle, maxillary/mandibular planes angle, upper and lower incisor inclinations, Y-axis, facial proportions (Mills, 1970), and the Holdaway angle. The M/M ratio is the ratio between the maxillary anq mandibular lengths described by Enlow et a/. ( 1969) and modified by Kerr and Adams, (1988), i.e. Point A-pterygomaxillary vertical/Point Bpterygomaxillary vertical. Skeletal I gives a value of 1. The Holdaway angle, Holdaway (1983), is the angle soft glabella/soft pogonion/labrale superius. A comparison of the mean values for the surgical and orthodontic groups is shown in Table 2. Males and females have been combined as no significant sexual dimorphism was found. The error of the method was calculated according to Houston ( 1983) as follows. Twenty-five randomly selected radiographs were digitiz~d on .a second occasion. Student's t-tests between first and
FIG. I Points plotted. I, basion; 2, sella; 3, ethmoid registration point; 4, nasion; 5, pterygomaxillare; 6, posterior nasal spine; 7, anterior nasal spine; 8, apex upper incisor; 9, incisal edge upper incisor; 10, point A; II, Incisal edge Lower Incisor; 12, Apex Lower Incisor; 13, point B; 14, gnathion; 15, menton; 16, gonion; 17, condylion; 18, soft glabella; 19, labrale superius; 20, soft pogonion.
TABLE 2 Comparison of means Variable
Surgery mean±sd
Orthodontics mean±sd
mean diff.
SNA" SN8° ANB' M/M ratio BaS No Goniar MMPA 0 Facial prop. 1/maxo /lmando Y-axiso Holdawayo
79·5±4·0 86·4±5·2 -6·9±2·9 0·78±0·07 126·6±6·1 133·3±8·3 25·3±7-8 55·9±3-6 115·4±7·8 78·5±9·9 61·9±4·5 0·9±4·4
81·2±2-4 83-8±3·3 -2·6±2·6 0·89±0·08 126·3±6·9 132·2±5·5 29·0±4·1 56·2±2·3 112·9±7·3 85·4±5·2 64·0±3-3 6·1 ±5·0
1·7 2·6 4·3* .. 0·11*** 0·3 1·1 3·7 0·3 2·5 6·9** 2·1 5·2**
•• P < 0·01; ••• P< 0·001.
second time means for the variables showed no significant differences, indicating no significant systematic error. Correlation coefficients between first and second times of measurement (range r=0·93l·O) indicated a low level of random error. Results
Four significant differences between the mean
Class III Malocclusion 23
BJO February /99]
values for the variables of the two groups were elicited. Angle ANB was significantly more negative in the surgical group; -6·9 degrees compared with -2·6 degrees (P
ISSN: 0301-228X (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/yjor19
Class III Malocclusion: Surgery or Orthodontics? W. J. S. Kerr M.D.S., D.Orth., F.D.S., F.F.D., S. Miller B.D.S., F.D.S. & J. E. Dawber To cite this article: W. J. S. Kerr M.D.S., D.Orth., F.D.S., F.F.D., S. Miller B.D.S., F.D.S. & J. E. Dawber (1992) Class III Malocclusion: Surgery or Orthodontics?, British Journal of Orthodontics, 19:1, 21-24, DOI: 10.1179/bjo.19.1.21 To link to this article: http://dx.doi.org/10.1179/bjo.19.1.21
Published online: 21 Jun 2016.
Submit your article to this journal
Article views: 3
View related articles
Citing articles: 19 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=yjor19 Download by: [Tufts University]
Date: 25 September 2016, At: 15:53
British Journal of Orthodontics/ Vol. 19/1992/21-14
Class III Malocclusion: Surgery or Orthodontics? W. J. S. KERR, M.D.S., D.ORTH., F.D.S., F.F.D. S. MILLER, B.D.S., F.D.S.
J. E. DAWBER Department of Orthodontics, Glasgow Dental Hospital and School, 378 Sauchiehall Street, Glasgow G2 3JZ Received for publication January 1991
Abstract. The pre-treatment lateral cephalograms of two groups of 20 subjects with severe Class Ill malocclusions were compared. One group had been considered suitable for orthodontic correction by the diagnosing clinician and the other offered orthognathic surgery. The most sign(ficant d(fferences between the groups were in angle ANB, M/ M ratio (P < 0·001), lower incisor inclination and Holdaway angle (P < 0·01). Threshold values .for angle AN Band lower incisor angulation below which surgery was almost always carried out were -4 and 83 degrees, respectively. Index words: Class III, Surgery, Orthodontic Appliances.
Introduction Surgery and orthodontics are not normally alternative treatments for the same Class III malocclusion. The decision as to which form of treatment is allocated to such patients is made with reference to the severity of the malocclusion and the prognosis for its correction by orthodontic means. Factors which are generally thought to influence the prognosis for orthodontic correction of anterior cross-bite are the degree of antero-posterior and vertical skeletal discrepancy, the inclination of the incisors and the depth of the overbite. A mild skeletal discrepancy, near normal inclination of the upper and lower incisors, which permits the appropriate adjustment of their angulations, and an initial overbite, deep enough to remain to some extent after correction of any anterior crossbite, are seen as favourable indicators of a good prognosis. The age of the patient and the potential for skeletal growth are also of significance in Younger individuals. The perception by the patient of their condition is an important additional factor, as in some cases the profile, rather than the malocclusion, is the principal cause of concern. Although the soft tissue profile may be improved to some degree by orthodontic treatment (Kerr and TenHave, 1987) the change may be too subtle to be appreciated by the untrained eye (Kerr and O'Donnell, 1990). Orthodontic appliances (fixed, functional, and 030 I· 228X/92/004000 + 00502.00
removable) generally bring about the correction of anterior cross-bite by varying amounts ofproclination of upper incisors and retroclination of lower incisors, combined with a degree of backward rotation of the mandible (Kerr and Ten Have, 1988). Proffitt and Ackerman ( 1985) have postulated the concept of three 'envelopes of discrepancy' representing the limits for what can be corrected variously by, orthodontic treatment alone, orthodontic treatment with growth and surgical treatment. Although no data was presented, the limits for incisal movement in the non-growing Class III cases would be an advance of 2 mm for the upper incisors combined with retraction of the lower incisors by 3 mm. The equivalent values for surgical movement were 10 and 25 mm. As far as orthodontic correction is concerned the initial incisor inclination will influence how much movement can be achieved and, hence, this knowledge alone is insufficient to be of much clinical assistance. The aim of this study was, therefore, to try and establish some cephalometric yardsticks which would enable the 'surgery or orthodontics' decision to be taken in a more objective way.
Materials The materials consisted of the pre-treatment lateral cephalograms of 40 patients, equally divided by sex, taken at the Glasgow Dental Hospital and Cannies(!) 1992 British Society for the Study of Orthodontics
22 W. J. S. Kerr eta/. TABLE I
BJO Vol. 19 No. I
Details of subjects included in the study
Males Females Total Mean age (years)
Surgery group
Orthodontics group
10 10 20 17·2± 1·6
10 10 20 14·1± 1·5
burn Hospital, who had been offered either surgical or orthodontic correction of their Class Ill malocclusion. The surgical group had all been seen by an orthodontist, who made the initial decision as to the need for surgery. The orthodontic group were among subjects successfully treated orthodontically forming part of a study previously reported (Kerr and TenHave, 1988). So that the malocclusions were of roughly comparable severity only subjects with negative overjets were included. The details are given in Table 1. Methods
Because two cephalostats with different magnification factors were used in taking the radiographs, and to eliminate sex differences due to size, points and measures were chosen to compare angular and proportional dimensions only. Twenty cephalometric points were digitized on each radiograph and these are demonstrated in Fig. 1. The definitions for these points are as described by Riolo et a/. ( 1974). Using PCDIG (McWilliam, 1989), a computer program which permits the construction of userdefined analyses, the following measurements were derived: SNA, SNB, ANB, M/M ratio, BaSN (cranial base angle), gonia) angle, maxillary/mandibular planes angle, upper and lower incisor inclinations, Y-axis, facial proportions (Mills, 1970), and the Holdaway angle. The M/M ratio is the ratio between the maxillary anq mandibular lengths described by Enlow et a/. ( 1969) and modified by Kerr and Adams, (1988), i.e. Point A-pterygomaxillary vertical/Point Bpterygomaxillary vertical. Skeletal I gives a value of 1. The Holdaway angle, Holdaway (1983), is the angle soft glabella/soft pogonion/labrale superius. A comparison of the mean values for the surgical and orthodontic groups is shown in Table 2. Males and females have been combined as no significant sexual dimorphism was found. The error of the method was calculated according to Houston ( 1983) as follows. Twenty-five randomly selected radiographs were digitiz~d on .a second occasion. Student's t-tests between first and
FIG. I Points plotted. I, basion; 2, sella; 3, ethmoid registration point; 4, nasion; 5, pterygomaxillare; 6, posterior nasal spine; 7, anterior nasal spine; 8, apex upper incisor; 9, incisal edge upper incisor; 10, point A; II, Incisal edge Lower Incisor; 12, Apex Lower Incisor; 13, point B; 14, gnathion; 15, menton; 16, gonion; 17, condylion; 18, soft glabella; 19, labrale superius; 20, soft pogonion.
TABLE 2 Comparison of means Variable
Surgery mean±sd
Orthodontics mean±sd
mean diff.
SNA" SN8° ANB' M/M ratio BaS No Goniar MMPA 0 Facial prop. 1/maxo /lmando Y-axiso Holdawayo
79·5±4·0 86·4±5·2 -6·9±2·9 0·78±0·07 126·6±6·1 133·3±8·3 25·3±7-8 55·9±3-6 115·4±7·8 78·5±9·9 61·9±4·5 0·9±4·4
81·2±2-4 83-8±3·3 -2·6±2·6 0·89±0·08 126·3±6·9 132·2±5·5 29·0±4·1 56·2±2·3 112·9±7·3 85·4±5·2 64·0±3-3 6·1 ±5·0
1·7 2·6 4·3* .. 0·11*** 0·3 1·1 3·7 0·3 2·5 6·9** 2·1 5·2**
•• P < 0·01; ••• P< 0·001.
second time means for the variables showed no significant differences, indicating no significant systematic error. Correlation coefficients between first and second times of measurement (range r=0·93l·O) indicated a low level of random error. Results
Four significant differences between the mean
Class III Malocclusion 23
BJO February /99]
values for the variables of the two groups were elicited. Angle ANB was significantly more negative in the surgical group; -6·9 degrees compared with -2·6 degrees (P
